Chip type variable electronic part and chip type variable resistor

ABSTRACT

In a chip type variable electronic part including an insulating substrate, and an adjustment rotor made of a metal plate rotatably mounted on an upper surface of the insulating substrate, in which the rotor is constituted of a first plate formed in a bowl shape to receive a screwdriver that rotates the rotor, and a second plate superposed on an upper surface of the first plate and integrally coupled thereto via a fold-back joint, and the second plate includes a screwdriver engagement hole perforated therein for the screwdriver to be fitted in, the fold-back joint is bent downward from an upper surface of the second plate, thereby preventing deformation of the fold-back joint when the rotor is rotated with the screwdriver.

TECHNICAL FIELD

The present invention relates to a chip type variable electronic partand a variable resistor constituted of an insulating substrate in theform of a chip, with a rotor for controlling the resistance value orcapacitance that is rotatably mounted on the upper surface of thesubstrate.

BACKGROUND ART

The chip type variable resistor which represents the variable electronicparts includes, as described in patent document 1 and as conventionallywell known, an insulating substrate formed in a chip type with a throughhole provided at a central portion of the substrate, a resistance filmprovided on an upper surface thereof in an arcuate shape concentric withthe through hole, an external terminal electrode corresponding to therespective end portions of the arcuate resistance film provided on theinsulating substrate, and an internal terminal electrode plate made of ametal plate adhered to a lower surface of the insulating substrate andincluding an integrally formed shaft portion that fits in the throughhole. On the upper surface side of the insulating substrate, anadjustment rotor made of a metal plate is rotatably mounted on an upperend portion of the shaft portion, and the rotor is constituted of afirst plate formed in a bowl shape to receive a screwdriver that rotatesthe rotor, and a second plate superposed on an upper surface of thefirst plate and integrally coupled thereto via a fold-back joint. Thefirst plate is provided with a sliding piece disposed in contact withthe resistance film, and a screwdriver engagement hole in which thescrewdriver is to be fitted is perforated in the second plate.

Also, in the conventional chip type variable resistor, as described inthe patented document 1, an internal terminal electrode plate disposedon the lower surface of the insulating substrate is provided with astopper piece formed to project upward from the upper surface of theinsulating substrate, so that when the rotor rotates the fold-back jointof the rotor is butted to the stopper piece, and a rotation angle of therotor is thereby delimited.

In the foregoing chip type variable resistor, the adjustment rotor is,as already stated, constituted of the first plate formed in a bowl shapeto receive the screwdriver that rotates the rotor, and the second platesuperposed on the upper surface of the first plate and integrallycoupled thereto via the fold-back joint, in which the first plate isprovided with the sliding piece disposed in contact with the resistancefilm, and the screwdriver engagement hole in which the screwdriver is tobe fitted is perforated in the second plate. In other words, rotatingthe second plate with the screwdriver inserted in the screwdriverengagement hole perforated therein causes the first plate provided withthe sliding piece disposed in contact with the resistance film torotate, with the sliding piece provided thereto maintained in contactwith the resistance film, and hence the fold-back joint between thefirst plate and the second plate is of a laid down U-shape, and therotation is transmitted from the second plate to the first plate viasuch fold-back joint, which leads to a problem that when rotating therotor with the screwdriver, the fold-back joint of the rotor is deformedsuch that the first plate and the second plate are shifted from eachother.

For this reason, the patented document 1 proposes increasing a widthwisedimension of the fold-back joint for preventing the deformation, howeverincreasing the width of the fold-back joint not only makes the foldingwork of the fold-back joint more difficult but also incurs an increasein weight, and besides when delimiting the rotation angle of the rotorby blocking the fold-back joint with the stopper piece, the rotationangle range is reduced to the same extent as the increase in width ofthe fold-back joint.

Also, for delimiting the rotation angle of the rotor the fold-back jointis butted to the stopper piece, and hence the stopper piece has to havea sufficient projecting height from the upper surface of the insulatingsubstrate to reach the fold-back joint, which incurs a problem that astrength of the stopper piece is reduced against tilting in a rotationdirection of the rotor thus being deformed, caused by the rotationthereof.

To increase the strength of the stopper piece against tilting, awidthwise dimension thereof may be increased in a rotation direction ofthe rotor, however increasing the width of the stopper piece not onlyincurs an increase in weight, but also results in reduction in rotationangle of the rotor, to the same extent as the increase in width of thestopper piece.

Patent document 1: JP-A-H11-354307

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

A technical object of the present invention is to provide a chip typevariable electronic part and a variable resistor in which the foregoingproblems are minimized.

Means for Solving the Problem

To achieve the technical object, a first aspect of the present inventionprovides a chip type variable electronic part including an insulatingsubstrate and an adjustment rotor made of a metal plate rotatablymounted on an upper surface of the insulating substrate; in which therotor is constituted of a first plate formed in a bowl shape to receivea screwdriver that rotates the rotor, and a second plate superposed onan upper surface of the first plate and integrally coupled thereto via afold-back joint, and the second plate includes a screwdriver engagementhole perforated therein for the screwdriver to be fitted in; wherein thefold-back joint is bent downward from an upper surface of the secondplate.

A second aspect of the present invention provides the chip type variableelectronic part according to the first, wherein the downwardly bentportion of the fold-back joint is formed to be butted to a stopper pieceprojecting upward from an upper surface of the insulating substrate.

A third aspect of the present invention provides the chip type variableelectronic part according to the second aspect, wherein the stopperpiece is an upwardly bent portion of an internal terminal electrodeplate disposed on a lower surface of the insulating substrate.

A fourth aspect of the present invention provides the chip type variableelectronic part according to the third aspect, wherein the stopper pieceincludes an abutment portion integrally formed therewith, to be incontact with the upper surface of the insulating substrate.

A fifth aspect of the present invention provides the chip type variableelectronic part according to any of the first to the fourth aspects,further comprising a resistance film of an arcuate shape concentric witha through hole provided on the insulating substrate; an externalterminal electrode corresponding to the respective end portions of theresistance film; and a sliding piece the adjustment rotor includesdisposed in sliding contact with the resistance film.

ADVANTAGES OF THE INVENTION

Since the fold-back joint is, as described in the first aspect, bentdownward from an upper surface of the second plate, the fold-back jointturns to be of an upright U-shape instead of the laid down U-shape, andthe rotation is transmitted from the second plate to the first plateunder the upright U-shaped configuration. In this case the transmissionefficiency of the rotational force is improved in comparison with thecase where the fold-back joint is of a laid down U-shape, andconsequently the fold-back joint can be reliably prevented from beingdeformed to shift the positional relationship between the first plateand the second plate, without increasing the width of the fold-backjoint as in the conventional variable electronic parts.

Also, as described in the second aspect, the downwardly bent portion ofthe fold-back joint is formed to be butted to a stopper piece projectingupward from an upper surface of the insulating substrate, which allowsforming the stopper piece in a lower projecting height from the uppersurface of the insulating substrate than in the case where the fold-backjoint is butted to the stopper piece, thereby effectively increasing thestrength of the stopper piece against tilting in the rotation directionof the rotor thus being deformed, without an increase in width of thestopper piece, and hence without incurring an increase in weight of therotor, and reduction in rotation angle thereof.

Further, since the stopper piece is an upwardly bent portion of aninternal terminal electrode plate disposed on a lower surface of theinsulating substrate as described in the third aspect, the formation ofthe stopper piece can be easily carried out utilizing the internalterminal electrode plate.

In this case, since the stopper piece includes an abutment portionintegrally formed therewith, to be in contact with the upper surface ofthe insulating substrate as described in the fourth aspect, theinsulating substrate is held by the stopper piece from an upper and alower direction, which leads to a further increase in strength of thestopper against tilting in the rotation direction of the rotor, and toreinforced adhesion of the internal terminal electrode plate to theinsulating substrate.

Especially, the configuration according to the fifth aspect isadvantageous in effectively achieving the foregoing effects in the chiptype variable resistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a variable resistor according to anembodiment of the present invention;

FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1;

FIG. 3 is a plan view showing a state where the rotor is rotated;

FIG. 4 is a cross-sectional view of a modified stopper;

FIG. 5 is a cross-sectional view of another modified stopper; and

FIG. 6 is a cross-sectional view taken along the line VI-VI in FIG. 5.

REFERENCE NUMERALS

1 chip type variable resistor

2 insulating substrate

3 adjustment rotor

4 internal terminal electrode plate

5 through hole

6 resistance film

7, 8 external terminal electrode

9 shaft portion

10 stopper piece

10′ abutment piece

11 first plate

12 fold-back joint

13 second plate

14 screwdriver engagement hole

16 sliding piece

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below referringto the drawings, in which the present invention is applied to a chiptype variable resistor (FIGS. 1 to 3).

In these figures, the reference numeral 1 designates a chip typevariable resistor. The chip type variable resistor 1 includes aninsulating substrate 2 in the form of a chip made of a heat-resistantinsulating material such as a ceramic, an adjustment rotor 3 disposed onthe insulating substrate 2, and an internal terminal electrode plate 4disposed on the lower surface of the insulating substrate 2.

The insulating substrate 2 is formed with a through hole 5 extendingfrom the upper surface to the lower surface of the substrate at agenerally central position, and a resistance film 6 disposed to extendthereon in an arcuate shape concentric with the through hole 5, and theinsulating substrate 2 is provided, on a lateral face 2 a thereof, withexternal terminal electrodes 7, 8 corresponding to the respective endportions of the resistance film 6.

The internal terminal electrode plate 4 is made of a metal plate anddisposed in close contact with the lower surface of the insulatingsubstrate 2, and includes a hollow shaft portion 9 integrally formedtherewith to be inserted into the through hole 5, and a stopper piece 10integrally formed therewith to be bent upward along another lateralportion 2 b of the insulating substrate 2.

The rotor 3 includes a first plate 11 made of a metal plate and formedin a bowl shape with a flange around an outer periphery thereof, and aplate-shaped second plate 13 integrally connected to the first plate 11via a fold-back joint 12, and the second plate 13 includes across-shaped screwdriver engagement hole 14 perforated therethrough, andis bent to be folded back at the fold-back joint 12 thus to besuperposed on the upper surface of the first plate 11, while the flangeon the outer periphery of the first plate 11 includes a slit hole 15perforated in a generally semicircular arc in a region opposite to thefold-back joint 12, and a portion of the flange radially outer from theslit hole 15 constitutes a sliding piece 16 to be brought into elasticcontact with the resistance film 6.

The rotor 3 is mounted on the upper surface of the insulating substrate2, such that a mounting hole 18 perforated in a bottom plate 17 of thefirst plate 11 of the rotor 3 is fitted over the hollow shaft portion 9,and then the lower surface of the bottom plate 17 is closely pressedagainst the upper surface of the insulating substrate 2 and the slidingpiece 16 is set in elastic contact with the resistance film 6, afterwhich an upper end portion of the shaft portion 9 is crimped to extendoutward, so that the rotor 3 is attached to the shaft portion 9 tofreely rotate around the shaft portion 9.

Then the fold-back joint 12 is bent downward, so that the downwardlybent portion is butted to the stopper piece 10.

Under such structure, the rotor 3 is rotated in left and rightdirections with a screwdriver inserted into the screwdriver engagementhole 14 of the second plate 13.

The rotational force of the screwdriver is first applied to the secondplate 13, and then transmitted to the first plate 11 via the fold-backjoint 12 connecting therebetween.

In this case, bending the fold-back joint 12 downward from the uppersurface of the second plate 13 erects the fold-back joint 12 to anupright U-shape instead of the laid down U-shape, so that the rotationis transmitted from the second plate 13 to the first plate 11 under theupright U-shaped configuration. Thus, the transmission efficiency of therotational force is improved in comparison with the case where thefold-back joint is of a laid down U-shape, and consequently thefold-back joint 12 can be reliably prevented from being deformed toshift the positional relationship between the first plate 11 and thesecond plate 13.

Also, when the rotor 3 is rotated to left and right, the downwardly bentportion of the fold-back joint 12 of the rotor 3 is butted to thestopper piece 10 as shown in FIG. 3, thereby delimiting the rotationrange of the rotor 3 within an angle of θ.

In this case, since the fold-back joint 12 is bent downward and suchdownwardly bent portion is naturally located closer to the upper surfaceof the insulating substrate 2, which allows forming the stopper piece10, to which the downwardly bent portion is butted, in a lowerprojecting height H from the upper surface of the insulating substrate 2than in the case where the fold-back joint 12 is not bent downward,thereby effectively increasing the strength of the stopper piece 10against tilting in the rotation direction of the rotor 3 thus beingdeformed, without an increase in width of the stopper piece 10.

Besides, a portion of the internal terminal electrode plate 4corresponding to the shaft portion 9 is made thinner, and a film 20 thatcovers the inside of the shaft portion 9 is adhered to the lower surfaceof the thinner portion, to prevent intrusion of a flux produced by asoldering process into an inner portion of the rotor 3, whenimplementing the resistor on a PCB or the like by soldering.

Further as shown in FIG. 6, the stopper piece 10 may include an abutmentportion 10′, integrally formed therewith to make contact with the uppersurface of the insulating substrate 2.

With such structure, the stopper piece 10 holds the insulating substrate2 from an upper and a lower direction with the abutment portion 10′ andthe internal terminal electrode plate 4, both integrally formed with thestopper piece 10, which significantly increases the strength of thestopper piece 10 against tilting in the rotation direction of the rotor3. Besides, the internal terminal electrode plate 4 is attached to theinsulating substrate 2 at two points, namely the portion of the shaftportion 9 integrally formed with the internal terminal electrode plate 4crimped over the rotor 3, and the abutment portion 10′ integrally formedwith the stopper piece 10 holding the insulating substrate 2, whichincreases the adhesion strength of the internal terminal electrode plate4 against the insulating substrate 2.

Still further, the stopper piece may be formed in a shape having aC-shaped cross-section, as a stopper piece 10″ shown in FIGS. 5 and 6.

1. A chip type variable electronic part including an insulatingsubstrate and an adjustment rotor made of a metal plate rotatablymounted on an upper surface of the insulating substrate, the rotorincluding: a first plate formed in a bowl shape to receive a screwdriverfor rotating the rotor; a second plate superposed on an upper surface ofthe first plate; and a fold-back joint for integrally coupling the firstplate and the second plate to each other; the second plate being formedwith a screwdriver engagement hole into which the screwdriver is fitted,wherein the fold-back joint includes a first portion and a secondportion, the first portion extending from the first plate, the secondportion extending from the second plate and being superposed on thefirst portion, both the first portion and the second portion being bentdownward from an upper surface of the second plate.
 2. The chip typevariable electronic part according to claim 1, wherein downwardly bentparts of the first portion and the second portion are formed to bebutted to a stopper piece projecting upward from an upper surface of theinsulating substrate.
 3. The chip type variable electronic partaccording to claim 2, wherein the stopper piece is an upwardly bentportion of an internal terminal electrode plate disposed on a lowersurface of the insulating substrate.
 4. The chip type variableelectronic part according to claim 3, wherein the stopper piece includesan abutment portion integrally formed therewith, to be in contact withthe upper surface of the insulating substrate.
 5. The chip type variableelectronic part according to any one of claims 1 to 4, furthercomprising a resistance film of an arcuate shape concentric with athrough hole formed in the substrate, and an external terminal electrodecorresponding to end portions of the resistance film, wherein theadjustment rotor includes a sliding piece held in sliding contact withthe resistance film.